Embodiments of the present invention generally relate to apparatus and methods for indicating seal leakage in a nozzle repair shield. More specifically, the present invention relates to apparatus and methods for directing material penetrating a leaking nozzle repair shield seal to a predetermined indication point such that a user viewing such indication point is alerted to the leaking seal condition.
In the chemical industry, use of glass or ceramic-lined reaction vessels for processing chemicals is often essential. For example, glass or ceramic-lined reaction vessels are used when the reactants and/or products of a reaction are highly corrosive as glass and ceramic are more tolerant of corrosive materials than carbon steel, stainless steel, metal alloys, or the like.
Additionally, glass or ceramic-lined reaction vessels are often used when the reactants and/or products of a chemical reaction are highly reactive as the surfaces of non-glass or non-ceramic (e.g., the surfaces of metal and alloy reaction vessels) can act as reaction sites for unwanted side reactions. Such side reactions may cause contamination of the end product as well as damage to the reaction vessel or its components. For example, an exothermic reaction may cause the maximum temperature of the reaction vessel or its components to be exceeded. This could result in damage to the components or breakage of the reaction vessel itself.
Although glass or ceramic reaction vessels can withstand corrosion and prevent side reactions, many of the reactions required for production of chemicals and other materials are performed under high temperature, high pressure, and/or vacuum conditions. Glass or ceramic reactions often cannot withstand such conditions. Therefore, it is common to line a carbon steel, stainless steel, or other metal alloy reaction vessel with glass or ceramic to allow the reaction vessel to be able to operate under corrosive and reactive conditions as well as under high temperature, high pressure, and/or vacuum conditions.
Maintaining the surfaces of a glass or ceramic-lined vessel is essential to ensure that the reaction vessel maintains its functionality as described above. The nozzles of glass and ceramic-lined reaction vessels tend to be more susceptible to damage than the other components of the reaction vessel. These nozzles are often used to attach valves, instrumentation, auxiliary equipment, feed piping, product piping, or the like. For example, the nozzles may be damaged when parts such as agitators, dip pipes, thermowells, or valves are broken during use. Alternatively, the nozzles may be damaged during the replacements of such parts.
Some apparatus and methods are known for repairing nozzles of glass and ceramic lined-vessels. Via one of the simplest methods, the damaged surface of the nozzle is first cleaned. If any rough edges exist, the nozzle surface is sanded such that a smooth surface results. Any recesses in the surface are then filled with a curable resin to ensure that there is no exposed metal. The nozzle and adjacent areas of the reaction vessel are then sheathed. Any gaps are filled with a curable resin.
Using one such repair method, the nozzle and adjacent area are sheathed with a two piece metal cover. The metal must be inert under the conditions of use of the reaction vessel being repaired. The cover is comprised of an outer and inner faceplate. The outer faceplate has a returning flange that covers the outwardly facing edge of the nozzle being repaired. The inner faceplate is crimped to the outer faceplate and covers the interior portion of the nozzle being repaired while mating with the outer faceplate. An inert gasket is also used to further secure the nozzle and cover.
Another known repair method includes sheathing the nozzle and adjacent area with a two piece, threaded metal cover. This method includes removing damaged portions of the nozzle with a cutting torch or the like. The remaining portion of the nozzle is then edge-tapered for welding. A replacement nozzle equivalent to the removed damaged portion is then welded onto the portion of the nozzle that remains. Next, the nozzle and adjacent portions of the reaction vessel are sheathed with a metal cover, wherein the metal is inert under the conditions of use of the reaction vessel being repaired. The metal cover includes inner and outer faceplates that are mated by threading the faceplates together.
Other similar repair methods include sheathing the nozzle and adjacent area with a machined polytetrafluoroethylene (“PTFE”) repair shield. One such repair shield includes a cylindrical body portion having an annular flange disposed from the top end and at least one sealing lip disposed at its lower end. The body portion further includes an annular support band located in its lower end for supporting the sealing lip during insertion and use. The shield further includes resilient spacing members between the sealing lips to minimize damage to the sealing lips and subsequent loss of a fluid-tight seal.
When repairing a damaged nozzle of a glass or ceramic-lined metal alloy reaction vessel, it is necessary to ensure that the repair device is completely sealed to the nozzle. If it is not, corrosive materials may seep between the repair device and the nozzle causing further damage to the nozzle. This damage may lead to the escape of the corrosive materials from the reaction vessel, which may in turn cause injury to nearby workers or damage to other components of the reaction system. Additionally, reactant and/or product loss could occur due to spillage. Without a proper seal between the repair device and the nozzle, the reaction vessel is also not likely to hold the required temperature, pressure, or vacuum, which is likely to prevent the needed reaction from occurring. Such reaction failure is also likely to result in reactant and/or product loss.